Hi, I just got a 1985 743 and it is in severe need of some work. One of the first major items is that it was missing the hydraulic filler cap and in the rain, it got a whole bunch of water in the hydraulic oil. Due to that, it is milky and I need to change it. How on earth do I do it? The service manual says to pull the filter and then disconnect the lines from the filter housing and it drains. I have done that, and almost nothing comes out. What am I missing? Anything else you would recommend? Thanks for your help! -d
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Other than removing the hydraulic tank to clean it out properly you could use a hand pump to pump it out,this is the method i used on my 743 when changing the oil.You dont want to run the machine if the oil is contaminated.Also when refilling use a good quality motor oil.I have done 10,000hrs on my 743B and always used Castrol RX Super 15w40 diesel engine oil in the hydraulics.
Jimbob, Thanks for the reply. Doesn't look that easy to remove. I know if I try to disconnect the tank, it is going to dump all of the oil before I can catch it. Sounds really messy. I guess I will try to pump it out of the tank What about the rest of the stuff in the pump and the lines? Do I just have to do several changes in a row? I planned on using ISO 46 Hydraulic fluid. From what I read, that seemed to be the closest to the Bobcat fluid. Any other tips? Seems like they made it really difficult to service these things. Thanks again! -d
lfutrell
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- May 29, 2011
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If you have one of the later (sn# after 5000) the port valve is mounted on the side rite behind the right steering lever, it has a temp sensor in it with a single wire going to it, if you remove that sensor the oil will drain from that to a catch pan setting underneath without any mess, of course it will not get all of the oil in the cylinders but it will drain the tank (about 4 gallons)
The only other way is to open a line at your aux couplers, pump it out. Run the machine at idle, operate the controls tll it starts to jitter and spit. Shut it down straight away. Remove teh hydraulic filter, drain it and put it back on.
Add say a bottle of oil, run it, drive it aroundm lift and tilt, this is to get fresh oil moving around mixing with the dirty oil. Drain the oil the same way. Do this till the oil is no longer milky. It will take a while, and the oil will be foamy which will appear to look like milk. When its looking pretty good, start collecting the oil in something you can re-use. If its pretty clean, you can use it in your chain case, no doubt it has been neglected too.
This will take a while, but you need to get all the oil out you can. The only other way is to remove everything and drain it, which really is not a great option. I have done it this way on a 753 with excellent results. It took about 4 cycles of this to get clean, but it wasn't really bad tio start with.
Not sure what oil the newer Bobcat's run like the 753's and S130's but i thought Bobcat brand oil was engine oil and a little thicker than hydraulic oil.The 743 had a vane pump instead of gear pumps like the newer machines and i think hydraulic oil might be too thin.Like Tazza said you can pump the contaminated fluid through the aux coupler but you do not want to run it dry.I really enjoyed the simplicity of the 743 and liked the fact you could use the same oil in the engine,hydraulics and chaincase,made it a lot easier to service and maintain.
Thanks for all of the advice. I tried the ISO 46 stuff and it made a the hydraulics make a whiny noise. I also didn't get all of the water out on the first try, so I am going to change it again with the motor oil. You mentioned Castrol RX Super 15w40. Does any 15w40 weight oil work? Anything special that I should look for in the oil? Thanks again!
Just a good quality engine oil would be fine,i noticed bobcat say to use 10w-30 or 10w-40 motor oil as a replacement to the oil in the hydraulics.Thats why i thought in the older machines bobcat brand oil was motor oil as i wouldn't recommend mixing hydraulic oil with engine oil.I would use the ISO 46 to flush all the water out then use motor oil.
